Rudd can be recognised by the golden-yellow iris, an upturned mouth, a keel between the anus and the pelvic fins, and the dorsal fin is set further back than in the case of the roach.
Rudd feed mainly on larvae, small crustaceans, water snails and other invertebrates, and will accept most baits offered by anglers, including bread. They feed at all depths, including on the bottom, but are most often caught in the upper layers of still waters.
There are two other varieties - The Lemon-finned Rudd, (lower picture) which as its name implies, has pale lemon fins and iris but otherwise has all the physical features of the red-finned form, and the Golden Rudd, a reddish gold sport in the wild, but also obtained by selective breeding and stocked in some fisheries.
Rudd can hybridise with roach (common) and with bream (less common) and also (rarely in the wild) with other cyprinids .